"We know we still have work to do," Vermes said, "but I think we've achieved something."

Talk about an understatement.

Sporting KC opened the season 1-6-1 before going on a dramatic worst-to-first run. They haven't lost in their last seven matches, and have scored in 21 of their last 22, a big reason why a sellout crowd of 18,565 showed up at Livestrong Sporting Park despite penetrating rain, winds whipping at 20 mph and temperatures that plummeted into the 30s during the second half.

Graham Zusi assisted on each of the goals for Sporting KC, which beat Colorado 2-0 on Sunday to open the two-game, aggregate-goal playoff. Sporting KC will host the Houston Dynamo or Philadelphia Union in the conference finals Sunday.

Houston won its first leg against Philadelphia, 2-1. They play again Thursday night.

"We made a point of talking about getting the first goal. We didn't want them to get that first goal and get some confidence," Zusi said. "That allowed us to settle down."

Collin scored in the 28th minute when he deflected Zusi's free kick, and Sapong returned from a scary collision in front of the net early in the second half to direct a perfect header past Colorado goalkeeper Matt Pickens in the 76th minute.

Sapong took off running for the corner in glee, sliding through the wet turf before the rest of his teammate piled on in joy. It was the start of what amounted to a 15-minute victory lap for Sporting KC, which is back in the Eastern Conference finals for the first time since 1997.

"We're here now because we've done it at the end of the season. That's big time," said Vermes, who played for the franchise back when it was the Wizards. "These guys have really stepped up. I couldn't be more proud of them."

It was a disheartening end to Colorado's season.

The Rapids had already lost Jamie Smith to a torn right ACL and Pablo Mastroeni to a concussion before three more players went down in Sunday's game. Striker Caleb Folan sprained his left ankle and knee, Kosuke Kimura fractured his left foot and Drew Moor separated his shoulder.

Tyrone Marshall also earned a red card Sunday, keeping him out of Wednesday's match and putting the reigning MLS Cup champions in quite a hole against the league's hottest team.

"Yes, we've been affected by the injuries, but the scoreline in six weeks' time, or two weeks' time, will suggest that we lost 4-nil," Colorado coach Gary Smith said. "Nobody will know what happened, nobody will know the injuries; 4-nil over two legs and they go through."

Things were chippy on the sloggy pitch from the start, but the fouls didn't cost either team until Colorado's Joseph Nane earned a yellow card for taking down Sapong in the 28th minute.

Zusi hammered the free kick from near midfield toward the Colorado net, and Collin backed up Pickens, almost as if he was posting up. Collin managed to somehow deflect the ball off the back of his head and into the net, giving Sporting KC a 1-0 lead.

"When you put a dangerous ball in the box like that, there's no telling what's going to happen," Rapids defender Wells Thompson said. "It definitely takes the wind out of your sails."

Early in the second half, Sapong tried to convert a bicycle kick in front of the Rapids goal and came down hard on his back. Colorado defender Marvell Wynne's knee inadvertently banged off the back of his head, and Sapong spent several minutes on the mushy turf before walking to the sideline.

He returned a few minutes later, and found a spot just inside the area in the 76th minute when Zusi wound up on a free kick. Sapong leaped up and headed home the goal, which amounted to an exclamation mark on a dominating two-game series against the Rapids.

"We have a competitive group," longtime Sporting KC midfielder Davy Arnaud said. "When you get to the playoffs, everything is magnified. We knew they were going to compete and battle, and we had to match that and more."